09/28/18: WordPress Plugin ACF Frontend Display 2.0.5

Threat Summary

Overview

The ‘ACF Frontend Display’ plugin is used for generation of custom field values callable via shortcodes in the WordPress platform. The plugin contains a file upload vulnerability whereby an attacker is able to upload arbitrary files via the vulnerable script acf-frontend-display/js/blueimp-jQuery-File-Upload-d45deb1/server/php/index.php. This is due to a lack of sanitization or authorization when accepting uploads. No authentication is required for successful exploitation of this vulnerability.

Exploitation

Stages

An attacker makes a form upload request to wp-content/plugins/acf-frontend-display/js/blueimp-jQuery-File-Upload-d45deb1/server/php/index.php containing php payload.

The plugin accepts the upload due to a lack of sanitization or authorization and moves the file to the public location wp-content/uploads/uigen_[CURRENT_YEAR]/[filename].php.

Prerequisites

Alert Logic Coverage

Alert Logic® has evaluated its customer base for exposure to the exploit and has developed signatures for mitigating the threat depending on the security service in place.

The Network-Based Intrusion Detection System (IDS) has been updated with the new signatures for this exploit when detected via Alert Logic Threat Manager™. If this signature is detected, an incident is generated in the Alert Logic console.

Recommendations for Mitigation

To mitigate the vulnerability, upgrade to a non-vulnerable version of the plugin.